What data is sent to the server?
Nothing. The data resides completely on your client device, be it a mobile device or a desktop computer. The functionality relies on HTML5 localStorage which means the data is only available from the domain storing it, even the subdomains can't access it.

Can I somehow move my data to another device and continue tracking there?
Unfortunately not at the moment. The service was designed security first which means the data is stored locally and is completely unavailable to anyone on different domain or different client device. This is however a planned improvement on the future.

I've got this brilliant feature idea, can I send it to you?
Yes! If you take a look at the page footer you'll find a link which you can use to send me bug reports and development ideas. I won't promise your idea will be implemented but it will be at least considered and I try to acknowledge every idea I get so that people know the idea has been received.